Let me give you a personal example of mine.
www.teenwebcams.in
Created in Dec, 2012. It went #1 immediately for terms:
teenwebcams
teen webcams
teen cams
free teen webcams
free teen web cams
free teen cams
For about 5 weeks it was gangbusters. About 3K in traffic a day that converted into a few sales a day. Then from late January to about April nothing.... Hard to find it. But then by May it was back for certain keyword combinations. Nothing like before, but that was the honeymoon period people speak of.
There are a lot of webmasters that create networks based only on the HP. Make mad money, then dump it and move on to more domains.